The PTC PT239X Echo Processor IC, widely utilized in audio applications for generating digital delays and modulations, finds frequent use in Karaoke mixers and similar devices requiring audio modulation.

Originating from Taiwan, the processors often incorporate passive components, primarily capacitors, not readily available globally. However, owing to the non-critical nature of their values, substituting with close alternatives is feasible. Operating on CMOS technology, the IC boasts a remarkably low distortion rate, typically less than 0.5%. Nonetheless, some designers have noted a slight buzzing noise during operation. Despite these limitations, the IC remains prevalent in audio consoles for echo functions. For further information, refer to the linked datasheet below.

The PT239 Seires are CMOS echo/delay processors developed by Princeton Technology Corp. These digital chips integrate an Analog-to-Digital Converter (ADC) and a Digital-to-Analog Converter (DAC). Initially conceived as a straightforward solution for adding delay/reverb/echo to karaoke setups and entertainment systems, they gained significant traction within the guitar pedal community. This popularity stems from their capacity to replicate BBD-based delay circuits, affordability, through-hole packaging, compatibility with 5V power supplies, and adaptability to modifications.

With meticulous design and calibration, this integrated circuit has proven to deliver exceptional sound quality. Numerous renowned effects, such as the Belton/Accu-Tronics reverb module, Danelectro FAB-Echo, and the Rebote Delay, leverage this chip as the cornerstone of their circuits.

Application

• Audio processing application
• Echo creator
• Karaoke Mixer
• Entertainment/Infotainment system
• Electronics toys

Features

• Audio Echo Processor for digital delay 
• Supply Voltage: 4.5V to 5.5V
• Power Supply Rejection Ratio: -40dB (typically) 
• Available in 16-pin PDIP, GDIP, PDSO packages

PT239X Series

The PT2399, a CMOS device, offers an experimenter-friendly interface within circuits. CMOS technology, compatible with other CMOS devices, simplifies prototyping without the need for a microcontroller. Its familiar DIP packaging facilitates integration into through-hole designs, but handle the PT2399 with care, as CMOS devices are susceptible to static electricity damage.

The Princetown PT239X Series comprises various ICs with similar capabilities, including the following popular options:

• PT2395: Featuring 40 pins, this variant necessitates external DRAM memory (IC 41256 or 4164). It supports short/long modes (64Kb or 256Kb RAM), offering a maximum delay of 800ms (extendable to 1.5s with noise). It boasts voltage-controlled delay time, with the shortest delay achievable around 10ms, making it unsuitable for chorus/flanger effects but ideal for long delay/echo applications.

• PT2396: With 24 pins, this model incorporates internal 48Kb memory. It requires an external 2MHz clock and sets delay time via serial data communication, necessitating a microcontroller. Offering a minimum delay of 12ms and a maximum of 192ms, its availability is limited.

• PT2399: This 16-pin variant reigns as the most popular due to its simplicity and widespread availability. Equipped with 44Kb internal RAM, delay time is adjusted using an external resistor, simplifying circuit design. It offers a minimum delay of 30ms and a maximum of 340ms.

The PT2399 is an easy-to-use audio signal processor adds a delay/echo effect to the signal passing through it. This chip is commonly used in guitar effects due to how relatively few external parts are needed to use it in-circuit. The PT2399 is a single chip echo processor IC utilizing CMOS technology. Which accept analog audio input signal, a high sample rate ADC transfer the analog signal into a bit stream then storage to internal 44Kbit RAM, after processing the bit stream will de-modulate by DAC and lowpass filter. Overall delay time is determined by internal VCO clock frequency, and user can easy to change the VCO frequency by changing the external resistance. The PT2399 performs low distortion (THD<-90dBV) characteristic for audio purpose, and pin arrangement and application circuit are optimized for easy PCB layout and cost saving advantage. The PT2399 is a CMOS single-chip echo processor IC. A high sample rate ADC converts the analog data into a bitstream, which is then stored in internal 44Kbit RAM. After processing, the bitstream is de-modulated by DAC and lowpass filter. The internal VCO clock frequency determines the overall delay duration, and the user can easily modify the VCO frequency by changing the external resistance.